Oscillating mirrors are employed to scan objects and raster-scan displays. Such a mirror is generally connected to two vibrating flexural beams, thereby forming a single degree-of-freedom (DOF) structure, wherein the structure has a single torsional resonance frequency. Such scanners oscillate according to a sinusoidal waveform. The high gain (i.e., large compliances) which is exhibited by a second order system at its natural frequency (when there is a small amount of damping), gives rise to a significant angular deflection under a moderate sinusoidal torque.
Sinusoidal motion of the mirror reflects the light beam in a non-uniform manner, thereby yielding non-uniform intensity and hence, a low level of performance. It is possible to improve the scanning performance, if the mirror oscillates according to a triangular waveform. However, the value of the torque which is to be applied to the mirror in order to provide oscillatory motion having the triangular waveform, is approximately two orders of magnitude greater than in the case of sinusoidal motion. In large scale applications, where large torques can be produced, it is possible to produce this additional torque. However in small scale applications, such as micro-electromechanical systems (MEMS), due to the inherently small dimensions and the limitation of the commonly used electrostatic excitation, it is much more difficult to provide the needed torque.